In order to reduce the cost of storage systems, vendors have begun to use “desktop class” (e.g., IDE or Serial ATA) disk drives in server applications and in enterprise class storage systems. Traditionally, so-called “enterprise” class disk drives with SCSI or Fibre Channel (FC) interfaces have been used in these type applications that typically demand high performance and high reliability. Enterprise class disk drives (e.g., SCSI and FC) are generally designed for high-performance, 24 hour a day/7 days a week (24/7) operation, and high duty cycle applications where a high number of I/O (input/output) operations per second are typically performed by the hard disk drives (e.g., databases, e-mail, transaction processing, web serving, etc.). These enterprise disk class disks are generally designed, manufactured, and tested to work reliably while meeting these demanding application requirements. Typically, enterprise class disk drives use 10,000 RPM (revolutions per minute) or higher spindle speeds, support average seek times under 5 ms (milliseconds), and have MTBF (mean time between failure) rates over 1 million hours based on 720 power on hours per month (24/7) operation and high duty cycle workloads (e.g., seeking, reading, or writing) in the 70–80% active range. These SCSI or FC disks generally cost 3 to 6 times more per gigabyte (GB) of capacity than IDE or Serial ATA disks.
As compared to the enterprise class disk drives, traditional desktop class hard disk drives (IDE or Serial ATA) are generally designed to meet lower performance and reliability requirements, for lower power-on hours per month, and lower duty cycle applications. Typical desktop IDE class disks use 7200 RPM or slower spindle speeds, support average seek times greater than 5 ms, have MTBF ratings in the 500,000 hour range based on less than 250 power-on hours per month and low duty cycle workloads in the 30% active range.
Most storage subsystems that are using desktop class IDE and Serial ATA disk drives are being marketed for use in low duty cycle applications such as data backup (i.e. tape replacement), archival data storage, or for so-called near-line storage of reference data (e.g., medical imaging, etc.), which is typically accessed infrequently but which is desired to be readily available when needed. These applications are targeted for the use of desktop class disks because of the inherent lower performance of these disks compared to SCSI or FC disks, as well as the inherent application characteristics for lower duty cycle usage.
Although storage systems that use desktop class disks may be marketed for use in applications that have low usage or duty cycle access patterns, there is nothing that prevents them from being used in applications that exceed the rated duty cycle of these disks. In this case, the storage system manufacturers can expect to see a much higher failure rate for these disks than would be normally expected, leading to higher warranty expenses, and lower overall profit over the life of the product. There are MTBF de-rating factors that would need to be applied based on actual power-on hours, actual duty cycle, etc., in order to determine the real expected reliability of these disk drives when used in enterprise applications. Also, customer expectations for quality may not be met due to excessive repair actions and potential loss of customer data due to multiple disk failures in a RAID-5 array of desktop class disks, for example.
Since the trend of using desktop class disks in enterprise storage applications is a recent occurrence in the industry, vendors have not recognized nor adequately addressed these issues. Accordingly, a need exists for improving the quality and reliability of desktop class disks in enterprise storage applications. The present invention addresses such a need.